Toughing it out: compressed air and vacuum for container glass production

Saint-Gobain Oberland AG is one of the leading manufacturers of container glass. Its Wirges/Westerwald factory in Germany produces some 1.5 million bottles per day, using huge quantities of compressed air in various compression stages. The compressed air is generated by extremely durable rotary vane compressors, which as well as requiring little maintenance are highly energy efficient.

Glass Witting Saint Gobain
Caution Hot: Molten glass at temperatures of over 1100°C is shaped into bottles and containers in forming plants.

Sand and soda, lime or dolomite and recycled glass: these are the ingredients used to manufacture bottles and glass containers. The process also requires very high temperatures and (compressed) air as a conveying and process medium - and on a vast scale, because the greater the production volume, the more cost-effective the processes.

Saint-Gobain Oberland AG, one of the giants in the sector, manufactures around 10 million glass packaging containers every day at its four German factories. Since 2010 the products have been marketed to the food and beverage industry under the Verallia brand. The Wirges factory in Westerwald produces some 1.5 million units per day.

Watching the production process unfold on a tour of the factory is impressive. Compressed air in various compression stages is involved in several phases of the process. It starts with the pneumatic conveying of the individual materials into the mixing plants.

After mixing, the powdered batch is introduced into one of two tanks, each with a capacity of some 300 metric tons, where it is melted at a temperature of around 1,600°C and then held at that temperature. The hot stream of molten glass discharged from the tank is divided into portions, and the redhot material is carried - again pneumatically - through ultra-heat-resistant troughs to the forming plant.

The forming process is supported by compressed air and vacuum: the hot material is pressed into the mold by compressed air, while the vacuum - draws - the glass up against the walls of the mold. Together they establish the conditions for uniform wall thicknesses.

The bottles are then cooled under controlled conditions. At the "cold end" - which in the glass container industry refers to temperatures below 600°C! - the bottles and containers are annealed, 100 % inspected, and packaged.

3,600 kW installed compressor power

With daily output running to seven figures, it's hardly surprising that the Verallia factory in Wirges uses huge amounts of compressed air. As Andree Merten, team leader for mechanical systems and media, explains: "We have two large compressed air stations with an installed compressor/vacuum pump power of around 3,600 kW." The air supply adjacent to the melting tanks is the biggest energy consumer in the production process, and the managers attach a corresponding degree of importance to energy-efficient compressed air generation. "The energy management system at the factory is certified to EN ISO 50001," says Andree Merten. "We record all energy usage data and utilize the results not only to optimize consumption but also for the purposes of preventive maintenance."

Glass Witting Saint Gobain
Rotary vane compressors from Gardner Denver Wittig generate compressed air for the 4-bar network.